Compare Chrome extensions: Unpaywall vs Open Access Button

Get full text of scholarly articles as you browse. When you view a research article, Unpaywall automatically looks for a copy in our index of 20 million free, legal fulltext PDFs. If we find one, click the green tab to read the article.

Unpaywall points you to legal, author-posted manuscripts that are hosted on university and government web servers. We are pointing to versions that have been posted with the full and explicit authorization of the publishers themselves.

These free, author-posted manuscripts are often called "Green Open Access" and are a longstanding and completely legal part of the scholarly communications ecosystem. The majority of scholarly journals permit authors to "self-archive" their papers on university and government web servers. It's these legally self-archived papers that Unpaywall helps users find. Any papers posted outside of publisher permissions are NOT included in our index.